| 摘要 |
PURPOSE:To ensure the registration compensation, by properly processing the detection signal after detecting an external magnetic field and then producing an optimum magnetic field to compensate the effect of the external magnetic field. CONSTITUTION:The Hall devices 18 and 19 are set close to each other to detect an external magnetic field, and the measurement is required with high accuracy for the component within a plane including three image pickup tubes 3, 4 and 5 of only the external magnetic field. Accordingly the devices 18 and 19 are isolated from a magnetic matter, a converging/deflecting coil, etc. that generates the magnetic field and positioned at the area where only the external magnetic field can be detected to be attached to a camera head to follow the direction of a camera. The relations are defined as shown by equations 1-3 between the magnetic field intensities Hy and Hz which are detected by the devices 18 and 19 and the magnetic field components HAR, HAG and HAB in the tube axial direction of the tubes 3, 4 and 5 respectively. The currents iR, iG and iB shown by equations 4-6 (K: sensitivity coefficient) are flowed to circular coils 26, 27 and 28 to compensate the change of magnetic field within the image pickup tube which is caused by the change of the external magnetic field. |
